Winter gas still has 10% Ethanol. The difference is that the oil companies put Butane in their blends to help cars start easier. I see you are in the Chicago area, they have stiffer rules on the Vapor Pressuse regulations versus what we do down state. Basically, your winter blend is what we run during the summer down here. So, I wouldn't be afraid of topping off the tank. I used to delivey gasoline and ethanol all over the midwest, I've been out of the game for a few years, but I'm sure it hasn't changed.
